The present invention relates generally to imaging systems and more particularly to an improved apparatus for dissipating heat in an imaging system.
Typical fixed X-ray tubes include a beam of electrons directed through a vacuum and across a very high voltage (on the order of 100 kilovolts) from a cathode to a focal spot position on an anode. X-Rays are generated as electrons strike the anode, which typically includes a fixed target track.
The conversion efficiency of X-ray tubes is relatively low, i.e. typically less than 1% of the total power input. The remainder is converted to thermal energy or heat. Accordingly, heat removal, or other effective procedures for managing heat, tends to be a major concern in X-ray system design.
Many X-ray systems include dielectric oil for dissipating heat from the anode. When dielectric oil gets hot, however, it expands. The pressure of the expanding oil must be relieved, or X-Ray tube heads will leak and/or rupture.
Without adequate cooling mechanisms, temperature of the dielectric oil reaches very high values that may limit the continued operation of the equipment in many ways. Some of the major ways operation may be limited include reductions in dielectric strength resulting in oil breakdown and degradation of the polymers used to package the high voltage (HV) X-ray circuit.
Current X-ray systems implementing bipolar technology, wherein positive and negative voltages are applied to an anode and cathode respectively, pose a special challenge for system cooling. Typically, this cooling is attempted through implementation of a rubber or metal membrane that flexes with the expanding dielectric oil.
A difficulty for membranes in X-ray systems is that they must meet stringent X-Ray leakage specifications. This inhibits free flow of oil within the equipment because openings in the X-Ray shield around the tube must be carefully managed to prevent X-ray leakage. Membranes tend to be susceptible to leakage.
Conventional X-ray systems also use oil pumps for drawing hot oil around the X-ray tube. The hot oil is then circulated through a heat exchange system. Heat exchangers tend to be large, heavy, noisy, and generally unreliable.
The disadvantages associated with current X-ray systems have made it apparent that a new technique for HV connection to X-ray systems is needed. The new technique should include robust response to thermal stress and should also prevent material degradation or oil leakage while still maintaining a superior HV performance. The present invention is directed to these ends.